1. Field
One embodiment of the present invention relates to a head used in a disk drive device provided with a disk recording medium based on the discrete track recording technique, a head suspension assembly provided with the head, and a disk drive device provided with the head suspension assembly.
2. Description of the Related Art
A disk drive device, e.g., a magnetic disk drive device, includes a magnetic disk disposed in a case, a spindle motor that supports and rotates the magnetic disk, a head that reads and writes information from and to the magnetic disk, and a carriage assembly that supports the head for movement with respect to the magnetic disk. The carriage assembly includes a rockably supported arm and a suspension extending from the arm, and the magnetic head is supported on an extended end of the suspension. The magnetic head includes a slider attached to the suspension and a head portion provided on the slider. The head portion is constructed including a reproducing element for reading and a recording element for writing.
The slider has a facing surface that is opposed to a recording surface of the magnetic disk. A predetermined head load directed toward a magnetic recording layer of the magnetic disk is applied to the slider by the suspension. When the magnetic disk drive device operates, an airflow is produced between the magnetic disk in rotation and the slider. Based on the principle of aerodynamic lubrication, a force (positive pressure) to fly the slider above the recording surface of the magnetic disk acts on the facing surface of the slider. By balancing this flying force with the head load, the slider is flown with a gap above the recording of the magnetic disk.
A magnetic disk of a discrete track recording (DTR) type has recently been proposed as a technique for improving the recording density of a magnetic disk drive device, as disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-283622, for example, and a development is being carried out for practical application. In a conventional magnetic disk, a magnetic recording layer is spread on a flat disk surface. On the other hand, the DTR magnetic disk is formed with a concave-convex surface, in which convex parts form magnetic recording tracks and concave parts form nonmagnetic grooves without magnetism. The convex parts are previously patterned to form a plurality of servo areas for servo data recording and data areas that enable a user to record data. Information is recorded or reproduced as a flying magnetic head traverses the concave-convex surface of the magnetic disk.
According to the DTR magnetic disk constructed in this manner, magnetic interaction between adjacent tracks is reduced by the nonmagnetic grooves, so that the recording capacity of the magnetic disk drive device can be increased. Since disk positioning reference signals (servo signals) can be formed as concave-convex patterns on the disk surface, there is an advantage that a servo write process is unnecessary.
In the data areas of the DTR magnetic disk described above, the convex tracks and the nonmagnetic grooves extend along the circumference of the disk, that is, along the moving direction of the head, and are alternately arranged radially of the disk. In the description to follow, the nonmagnetic grooves of the data areas will be referred to as “transverse grooves”.
On the other hand, the servo areas of the DTR magnetic disk are each originally formed of a plurality of portions, including a preamble portion, an address mark portion, a burst portion, etc., and their concave-convex patterns are complicated. Only the preamble portion will now be described for the sake of simplicity. In the preamble portion, nonmagnetic grooves are formed radially of the disk, and these nonmagnetic grooves extend substantially at right angles to the transverse grooves of the data areas. In the description to follow, the nonmagnetic grooves of the servo areas will be referred to as “longitudinal grooves”.
If the magnetic head slider flies above the disk that has those physical irregularities on its surface, a gap between the magnetic head slider and the disk changes depending on the irregularities of the disk surface. Thus, the flying height of the slider varies to compensate for the change of the gap.
If the disk surface is formed only of concave-convex configurations that, like the data areas, are based on a predetermined area ratio (land-groove ratio) between the concave and convex parts, the flying height variations of the slider are constant and unidirectional (flight reduction over a data surface). Therefore, no substantial problem arises if the slider flight is designed in previous consideration of the flying height variations.
Actually, however, the servo areas and the data areas are different in concave-convex configurations. If the slider passes their boundaries, therefore, the flight stability of the slider is impaired, and in the worst case, the reliability of the device is lowered considerably. If the flying height of the slider is reduced too much, in particular, the slider and the disk contact each other, so that data corruption or the like is caused to lower the reliability of the magnetic recording device, and this situation must be avoided.
Accordingly, the head that is combined with the DTR magnetic disk is expected to have a flight performance insensitive to change of irregularities that occurs when the head moves from the data areas to the servo areas and from the servo areas to the data areas.
In general, a slider is constructed so that a maximum positive pressure is produced at a trailing pad portion on its outflow end side on which recording and reproducing elements are disposed. If the pressure varies at boundaries between servo areas and data areas of a magnetic disk, in this case, it is difficult to suppress a reduction of the flying height of the slider.